Operating circuit for high pressure arc lamp



Feb. 23, 1960 D 2,926,287

OPERATING CIRCUIT FOR HIGH PRESSURE ARC LAMP FilSd Dec. 18; 1953 INVENTOR.

LESTER F. 8! RD ATTORNEYS Stfltes Parent dustries, Inc., Newark, NJ., a corporation of New Jersey Application December 18, 1958, Serial No. 781,222 4 Claims. or. 315-174) The invention deals with an operating circuit for high pressure are lamps and more particularly with an OPER- ating circuitfor compact type are lamps.

It has been found from life tests on high pressure arc lamps of the compact type that unnecessary instantaneous. current demands from the electrodes considerably shorten the life o'f'such lamps. The circuits that maintain peak currents at the lowest value yield the best useful life for the lamp. With a ballast for the are composed ofa simple reactance there is no compensation for'varying" light voltages and the light from the lamp will 'vary with the supply voltage. I

It is an object of the present invention to provide a circuit fo'r theoperation of compact arc lamps which greatly: increases the useful life of the lamps and render the light: output essentially independent of variations in the supply line voltage. It is another object of the present inven-' tion to provide a circuit for high pressure arc'lamp oper-- ation and including a linear inductance in series with thearc lamp so that the lamp currents may be controlled to closely approximate a- -sine wave. It is afurther object of the present invention to provide an operating circuit for compact type are lamps having-a ballast and means to compensate for line voltage to maintain a steady light outpu t.- Other objects'and-advantages of the present invention will become apparent from the description hereinafter following and the drawing forming a part hereof which illustrates the operating circuit of. this invention;

Compensation for changes in the supply line voltage must be theresult of a change in the impedance of the lamp circuit. Since the lamp is fixed in connection with its voltage rating, all co'ntrol for the lamp output must take place in the ballast-reactance. The invention, therefore, comprises a circuit including means by which the ballasting reactance is automatically varied in value and amount .to. maintain constant current in the lamp.

' The voltage consumed in certain arc'lamps is commonly about 50 percent to 60 percent of the supply line voltage and the remainder is absorbed in the ballast. The voltage across the alternating current lamp has a different phase relation with time than that across the ballast reactor and they are essentially 90 apart electrically. For this reason. the following table shows variations in voltage across the lamp and a ballast reactance with different line voltages.

Table Line Volt- Lamp Reactance age Voltage Voltage 2,926,287 Patented'Feb. 23, 1960 ballast for the arc, the circuit of the invention comprises a dual magnetic amplifier arrangement using one of its units to deliver half of the alternating current wave and the other of its units to deliver the other half. In some cases it may be desirable to use additional reactance in series relationship with the magnetic amplifier units to cover a particular range needed for control. The changes in reactance in these units are brought about by variations in the direct current supplied to the control windings of the amplifiers. Changes on the order of one to ten in reactance are" easily secured and with a minimum of power. The amount of direct current power is dependent upon the range of change in reactance needed, but in any case it is only a very small amount compared with the power that can be controlled on the alternating current side. The reactance is highest when the direct current isweakest and the reactance is lowest when the direct current is at a maximum. For this reason it is notpossible to operate the .direct current controls of the amplifier using only the supply lines and a rectifier system. In such case the results-would be-opposite from those needed. An increase in line voltage would cause an increase in direct current in the reacto'r. control windings and so reduce the reactance and increase the current. This is opposite to'the effect desired.

The control supply of the invention is a differential system comprising a voltage stabilizer means which delivers essentially constant voltage from 'anysupply voltage. By way of example, a saturable transformer and loading capacitor combination is" arranged to provide an output voltage which is constant within about 2 percent with changes of input voltage of 20 percent or 30 percent. Theoutput voltage from the transformer-capacitor-net .workfii's, therefore, maintainedclose to 130 volts'and' is connected to'agrecti'fying system, for example, a bridge type or full wave rectifier. The voltage supply tothe rec tifieris, therefore, the differential voltage between the stabilized voltage and the supply line voltage. Should the supply line voltage have a value of volts, there is then a' difference of 30 volts supplied to the rectifier and amplifier system, which represents the differential voltage between the steady source 'and the supply line. When the supply line'voltage is volts, the difference is 15 volts, which is supplied to the rectifier and the magnetic amplifier system.

' When the supply line voltage is volts, there is no direct current supplied to the magnetic amplifier windings and a reactance is at a maximum. When the supply line voltage is decreased, the increased amount of direct cur: rent in the amplifier windings reduces the reactance in the lamp circuit and permits more current to flow. It is possible therefore to accomplish the control of the lamp current so that a steady current results.

Referring to the illustration, the circuit of the invention comprises input lines 1 and 2 connectable to a source of line voltage. A transformer 3 forms a part of the voltage stabilizing system of the invention and comprises a primary winding 4 connected across the input lines 1 and 2. Conductors 5 and 6 are connected to the terminals of secondary winding 7 of the transformer 3. A capacitor 8 is connected between the conductors 5 and 6 across the secondary winding 7. One output conductor 9 of capacitor 8 is connected to the input lead 2. Another output conductor 10 of capacitor 8 is connected to an input terminal 11 of a full wave or bridge-type rectifier 12. The other input terminal 13 of rectifier 12 is connected to the other input line 1. The two output terminals 14 and 15 of rectifier 12 are each connected to a magnetic amplifier 16 and 17, respectively by means of conductors 18 and 19, which are connected to the control windings 20 and 21, respectively, of the magnetic ant.-

plifiers. The dual, windings 22 and 23 of the amplifiers are connected to one of the leads 1 in a physical parallel arrangement and are rectified for the passage of current therethrough in opposite directions so that one of the windings 22 and 23 deliver one-half of the alternating current of line 1 and the other winding delivers the other half o the, alternating current, each winding 22 and 23 having its reactance controlled, by its associated control winding 20; or 21. The dual amplifier windings are connected to electrode 24 of the compact arc lamp 25. The lead 2 is connected to the other electrode 26 of the compact arc lamp. The electrodes 24 and 26 of lamp 25 being spaced apart less than about one centimeter in an envelope containing an ionizable atmosphere of at least about one atmosphere pressure when, the lamp is cold. The lamp, is providedwith an ignition system comprising avsecondary coil27 of a pulse type high frequency ignitiontransformer (not shown) and a by-pass, capacitor 28 for the high frequency components.

As soon as voltage is applied to input leads. 1. and 2 it appears'also across the lamp 25. The transformer 3 is. excited and voltage appears across the capacitor 8,. This.

voltage is fixed, or stabilized, e.g. at 130 volts, as above described, and independent of the supply voltage. 'The diiferential voltage between the suppley volt-age and the stabilized voltage isapplied to the; rectifier 12 where it is rectified and appliedto control windings 20 and 21 of largeamounts of. power in the lamp with, the meet only a small amount in the amplifier control. Forthis reason the system is very economical and useful for compactarc lamp current systems."

Modifications of the operating circuit above described are contemplated within the scope of the appended claims.

What is claimed is:

1. An operating circuit for a high pressure are lampcomprising electrical input lines connected. to the electrodes ofthe arc lamp-andconnectable to a source of alternating current, a transformer comprising primary and secondary windings, the primary winding being connected across the input lines, a capacitor electrically connected across the terminals of the secondary winding, an output conductor of said capacitor connected to one of the input lines, a rectifier comprising input terminals and output terminals, a second output conductor of said capacitor connected to one of the rectifier input terminals, another input terminal of the rectifier being connected to the other input line, a magnetic amplifier comprising dual control windings connected to each other and each magnetically associated with a ballast winding, one of the control windings being connected to a rectifier output terminal, the other control winding being connected to another rectifier output terminal, the ballast windings being connected in one of the input leads in a physical parallel arrange ment in series with the lamp, and oppositely poled'rectifier means associated respectively with said ballast windings, whereby one of the ballast windings delivers one half wave of alternating current and the other ballast winding delivers the other half wave.

2. An operating circuit for a high pressure are lamp comprising electrical input lines connected to the electrodes of the arc lamp and connectable to a source of alternating current, a transformer comprising primary and secondary windings, the primary winding being connected across the input lines, a capacitor electrically'connected across the terminals of the secondary winding, an output conductor of said capacitor connected to one of the input lines, 'arectifier comprising input terminals and output terminals, a second output conductor of said capacitor connected to oneof the rectifier input'terminals, another input terminal of the rectifier being connected to the other input line, and magnetic amplifier means connected in series with the lamp.

3. An operating circuit for a high pressure arc lamp comprising electrical input lines connected to the electrodes of the arc lamp and. connectable to a source of alternating current, a saturable transformer including primary and secondary windings, the primary winding being connected across the input lines,'acapacitor electrically connected across the terminals of the secondary winding, an output conductor of said capacitor connected to one'of the input lines, a rectifier comprisinginput terminals and output terminals, a second output conductor of said capacitor connected to one of the rectifier input terminals, another input terminal of the rectifier being connected to the other input line, magnetic amplifier means'connected'in series with the'lamp, and means for controlling the impedance of said magnetic amplifier in accordance with the output of said rectifier.

4; An operating circuit according to claim 2, comprising ignitio'n means in series with said lamp and located inone of the input leadsbetween the amplifier means and thelamp.

References Cited in the file of this patent UNITED STATES, PATENTS 2,757,318 Noel et al. July 31, 1956 

